Which of the following is not an example of a chain-growth polymer?

$A$ metallic square loop $ABCD$ is moving in its own plane with velocity $v$ in a uniform magnetic field perpendicular to its plane as shown in the figure. Electric field is induced:

If $PM$ is the perpendicular from $P(2, 3)$ onto the line $x+y=3$,then the coordinates of $M$ are

$A$ parallel plate capacitor with air between the plates has a capacitance of $9 \, pF$. The separation between its plates is $d$. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant $K_1 = 3$ and thickness $d/3$,while the other one has dielectric constant $K_2 = 6$ and thickness $2d/3$. The new capacitance of the capacitor is .... $pF$.

In a unilocular ovary with a single ovule,the placentation is

$A$ police car with a siren of frequency $8 \, kHz$ is moving with uniform velocity $36 \, km/hr$ towards a tall building which reflects the sound waves. The speed of sound in air is $320 \, m/s$. The frequency of the siren heard by the car driver is .... $kHz$.